Studies are in progress to examine the mechanisms whereby afferent stimuli from the peripheral and central chemoreceptors are integrated within the brainstem respiratory controller. These studies are concomitantly examining processes which may be responsible for the neurogenesis of respiration. Three experimental series are now in progress or planned for the year. The first involves a comparison of changes in activity of pontile and medullary respiratory units resulting from hypercapnia, isocapnic hypoxia and pharmacological stimulation of the carotid chemoreceptors. The magnitude of these three stimuli are adjusted so as to produce equivalent alterations. In a second study, we are comparing the response of single phrenic nerve fibers to hypoxia and hypercapnia induced ventilatory changes. The aim of these experiments is to determine if the pattern of phrenic nerve activation differs dependng upon the stimuli to ventilation. Finally, a series of experiments is planned to assess if the medulary respiratory nuclei exert only integrative functions in ventilatory control or if these sites also have a primary function in the neurogenesis of ventilation. These experiments will involve an assessment of activity in single phrenic nerve fibers and in brainstem respiratory units of the medullary preparation having a brainstem transection at the pontomedullary junction.